{Mjagkova Jana. 12.09. maximum is vozm}

program maxkol-vo;

{$APPTYPE CONSOLE}

uses
  SysUtils;

var

n,i,m: integer;


begin
 readln(n);
 m:=0;
   If n mod 2=0 then
     begin
       For i:=1 to (n div 2) do
         m:=m+2*i;
     end;
   If n mod 2=1 then
     begin
       m:=m+3;
       For i:=1 to (n-3) div 2 do
         begin


           m:=m+2*i+3;
         end;
     end;
 Writeln(m);
 Readln;
end.
